Structure solution and refinement of stacking-faulted NiCl(OH)

Two samples of pure NiCl(OH) were produced by hydrothermal synthesis and characterized by chemical analysis, IR spectroscopy, high-resolution laboratory X-ray powder diffraction and scanning electron microscopy. Layers composed of edge-sharing distorted NiCl_6x(OH)_6−6x octahedra were identified as the main building blocks of the crystal structure. NiCl(OH) is isostructural to CoOOH and crystallizes in space group Rm [a = 3.2606 (1), c = 17.0062 (9) Å]. Each sample exhibits faults in the stacking pattern of the layers. Crystal intergrowth of (AγB)(BαC)(CβA) and (AγB)(AγB) [C6 like, β-Ni(OH)₂ related] stacked layers was identified as the main feature of the microstructure of NiCl(OH) by DIFFaX simulations. A recursion routine for creating distinct stacking patterns of rigid-body-like layers in real space with distinct faults (global optimization) and a Rietveld-compatible approach (local optimization) was realized and implemented in a macro for the program TOPAS for the first time. This routine enables a recursive creation of supercells containing (AγB)(BαC)(CβA), (AγB)(AγB) and (CβA)(BαC)(AγB) stacking patterns, according to user-defined transition probabilities. Hence it is an enhancement of the few previously published Rietveld-compatible approaches. This routine was applied successfully to create and adapt a detailed microstructure model to the measured data of two stacking-faulted NiCl(OH) samples. The obtained microstructure models were supported by high-resolution scanning electron microscopy images.

Computing details

(I)

Crystal data

ClHNiO	V = 156.58 Å^3
Mr = 111.15	Z = 3
Trigonal, R3m	Dx = 3.66 Mg m^−3
a = 3.26061 (8) Å	Mo Kα radiation, λ = 0.70930 Å
c = 17.0062 (9) Å	T = 295 K

Data collection

'Bruker D8-Advance, Debye-Scherrer mode, MPI-FKF, Stuttgart, Germany' diffractometer	Data collection mode: transmission
Johannson Ge(220) primary beam monochromator	Scan method: step
Specimen mounting: '0.5 mm glass capillary'	2θmin = 2.0°, 2θmax = 60.0°, 2θstep = 0.005°

Refinement

Rp = 0.050	χ^2 = 3.568
Rwp = 0.067	Profile function: Fundamental parameters
Rexp = 0.036	42 parameters
R(F^2) = 0.0200	Background function: 'Chebyshev polynomial'

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq	Occ. (<1)
Ni1	0	0	0	1.21 (2)
O1	0.33333	0.66667	0.0350 (2)	0.44 (3)	0.5
Cl1	0.33333	0.66667	0.08790 (8)	0.44 (3)	0.5

Geometric parameters (Å, º)

Ni1—O1	1.9744 (11)	Ni1—Cl1	2.4038 (9)
O1^i—Ni1^i—Cl1^i	20.9 (1)

Symmetry code: (i) −x, −x+y, −z.